Pulse width modulation fan

ABSTRACT

An apparatus can include a fan including a control pin. The fan may receive a pulse width modulated (PWM) signal at the control pin. The fan may further control a speed of the fan based on a duty cycle of the PWM signal when the PWM signal is in a first range and, responsive to the duty cycle of the PWM signal being in a second range, transmit information corresponding to the fan to an external controller.

BACKGROUND

A fan can be utilized in a computing environment to create flow within afluid, such as air. For example, a fan may be provided to the computingsystem to create flow across or along computing components in acomputing environment to cool such computing components. A fan canoperate based on signals received to pins coupled to the fan. At leastone pin can provide a pulse width modulation signal to a pin of the fanto operate the fan or abort operation of the fan.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a block diagram in the form of an example apparatusincluding a fan consistent with the disclosure.

FIG. 1B illustrates a block diagram in the form of an example apparatusincluding a fan and a sensor consistent with the disclosure.

FIG. 2 illustrates a block diagram in the form of an example apparatusincluding a fan control component consistent with the disclosure.

FIG. 3 illustrates a block diagram in the form of an example systemincluding a fan and a fan control component consistent with thedisclosure.

FIG. 4 illustrates a curve depicting an example of revolutions perminute versus pulse width modulation consistent with the disclosure.

FIG. 5 illustrates an example timing diagram including an initiationsignal consistent with the disclosure.

FIG. 6 illustrates an example timing diagram including an initiationsignal and information transfer sequence consistent with the disclosure.

FIG. 7 illustrates an example machine-readable medium for a pulse widthmodulation fan consistent with the disclosure.

DETAILED DESCRIPTION

One or more fans can be utilized in a computing system to provide fluidflow management to computing components in the computing system. Suchfans can include a plurality of pins that can receive various signals inthe course of operating the fan. The signals may be provided to the fanfrom an external controller such as a fan control component. In thecourse of operation, the fan or fans of the computing system mayencounter issues such as degraded performance, failures, or other issuesthat can give rise to sub-optimal fan performance.

In order to remedy these and other issues, troubleshooting measures maybe taken to determine a cause of the issues encountered by the fan orfans. Once the cause of the issue(s) is determined, the fan may berepaired, or the faulty fan may be removed, and a new fan may beinstalled. However, determining the cause of the issues can, in someapproaches, include physical inspection of the fan(s) to determineinformation corresponding to the fan(s).

Physical inspection of the fan(s) can be undesirable, however, becausein some approaches, physical inspection of the fan(s) can include a useror technician traveling to the location of the computing system in whichthe fan(s) is deployed. This can further include shutting down thecomputing system in which the fan(s) is deployed while the physicalinspection takes place, which can incur system downtime and/or loss ofcomputing resources to users of the computing system. These undesirableoutcomes can incur costs in the form of technician compensation for timein physically inspecting the fans, as well as costs in the form ofcomputing downtime, which can affect users of the computing system in anegative manner.

In contrast, examples described herein can provide apparatuses, methods,and/or machine-readable media that can allow for remote determination ofinformation corresponding to the fan(s) in a computing system. Forexample, examples herein can allow for a communication sequence to becarried out between a fan and a fan control component in whichinformation corresponding to the fan is transferred from the fan. Theinformation can be used to track and/or analyze fan failures, amongother things.

In some examples, the information corresponding to the fan can beutilized to predict fan errors or faults and/or may be used to determinepre-failure information for the fan. For example, if it becomes knownthat a particular lot of fans from a particular vendor are experiencingproblems or issues, the information corresponding to the fan could bepolled to take preemptive action to remedy potential faults in the fansbefore they actually occur. Such preemptive action could be taken, forexample in response to a recall notice from the vendor, or could bebased on knowledge that fans that were made at certain times or bycertain vendors are more prone to certain faults or issues.

In some examples, as described herein, a specific duty cycle value orrange of duty cycle values for a pulse width modulation (PWM) signal maybe reserved for use in communicating an instruction to the fan totransfer information about the fan to an external location such as a fancontrol component. For example, the fan may be configured to interpretthe duty cycle of the PWM signal exceeding a threshold value of thetotal PWM range that the fan is capable of receiving as such aninstruction. Responsive to receipt of PWM signals whose duty cycleexceeds this threshold value (which may be a percentage of the total PWMrange corresponding to the fan and/or a PWM value that corresponds to aparticular revolutions per minute (RPM) value the fan(s) is to operateat), the fan may transfer information corresponding to the fan to anexternal location such as a fan control component. As used herein, a“PWM signal” refers to a pulse width modulated signal that is assertedon a pin of a fan to control a speed at which the fan operates in someinstances and is asserted on a pin of a fan to initiate a transfer ofdata from the fan in other instances.

This can allow for information corresponding to the fan to be accessedremotely without the assistance of a technician, for example. Further,by utilizing existing pins of the fan to perform various aspects of thepresent disclosure, costly increases in connector size and/or redesignof the fan(s) to add additional pins or other communications channelsmay be avoided, for example. In addition, by selecting the thresholdvalue at which a PWM signal can initiate the transfer of informationcorresponding to the fan(s), the chance that the fan will misinterpretthe signal as a signal to perform a different operation can be minimizedor eliminated. For example, by reserving a particular range of PWMsignal values to initiate the transfer of information that is differentfrom a range of PWM signal values that are utilized to operate the fan,it may be possible to ensure a dichotomy between operation of the fanand transfer of information from the fan.

Examples of the disclosure include apparatuses, machine-readable media,methods, and systems related to a pulse width modulation fan. In someexamples, an apparatus can include a fan including a control pin. Thefan may receive a pulse width modulated (PWM) signal at the control pin.The fan may further control a speed of the fan based on a duty cycle ofthe PWM signal when the PWM signal is in a first range and, responsiveto the duty cycle of the PWM signal being in a second range, transmitinformation corresponding to the fan to an external controller.

FIG. 1A illustrates a block diagram in the form of an example apparatus100 including a fan 102 consistent with the disclosure. The fan 102 caninclude a plurality of pins 103, 105, 107, and 109 to receive and/ortransmit various signals in the course of operation. The fan 102 caninclude control circuitry 117 to control operation of the fan 102. Thecontrol circuitry can include logic, for example in the form of a fieldprogrammable gate array or application specific integrated circuit thatcan monitor the pins 103, 105, 107, and 109 of the fan 102 to determinecharacteristics of signals asserted to the pins 103, 105, 107, and/or109 to control operation of the fan.

In some examples, a first pin 103 can be a PWM pin to receive PWMsignals from an external source such as the fan control component 204illustrated in FIG. 2, herein. As used herein, a “PWM pin” is a pin ofthe fan 102 that is configured to receive PWM signals asserted theretofrom an external source. For example, a PWM pin (e.g., the first pin103) can receive a pulse width modulated signal that is asserted on PWMpin of the fan 102 to control a speed at which the fan 102 operates insome instances and is asserted on a pin of the fan 102 to initiate atransfer of data from the fan 102 in other instances. In general, thefan 102 may control its speed based on the current duty cycle of PWMsignal received at the first pin 103. However, a specific range of dutycycles (called the “second PWM range” or “second range of duty cycles ofthe PWM signal” below) may be reserved for requesting fan informationrather than for controlling fan speed. For example, the first pin 103can receive a signal in a first PWM range (e.g., a duty cycle of the PWMsignal being in a first range) to cause the fan to operate in a normalmode of operation (e.g., a mode of operation in which the fan is on oroff to provide fluid flow management to a computing component orcomputing system), and the first pin 103 can receive a signal in asecond PWM range (e.g., a duty cycle of the PWM signal being in a secondrange) to initiate a data transfer operation using a different pin(e.g., the second pin 105). The first pin 103 can be referred to hereinas a “control pin.”

In general, PWM signals contain a train of pulses in repeating pulseperiods, and convey information by controlling the durations (widths) ofthe pulses. The “duty cycle” of a given pulse is the proportion of thetotal pulse period during which the pulse is asserted. For example, FIG.5 illustrates an example PWM signal 532 (or pulse 532) that has a dutycycle of around 30%, meaning that the pulse is asserted for around 30%of the period. Since the PWM signal is made up of these pulses, the PWMsignal may also be referred to as having a duty cycle, which at anygiven moment is equal to the duty cycle of the most recently receivedpulse (or collection of pulses).

In some examples, the first PWM range and the second PWM range cancorrespond to different ranges of duty cycles. For example, the firstPWM range can correspond to fan duty cycles of 90% or less, while thesecond PWM range can correspond to fan duty cycles between 90% and 100%,as described in more detail in connection with FIG. 4, herein. Examplesare not so limited, however, and the first PWM range and the second PWMrange can correspond to different ranges of fan duty cycles than thoseexplicitly enumerated above.

The second pin 105 can be a fault signal pin, which can be used in somemodes of operation to transmit a fault signal from the fan 102 and inother modes of operation to transmit information corresponding to thefan 102, as described in more detail, herein. For example, responsive toreceipt, by the first pin 103, of a PWM signal within a first PWM range,the second pin 105 can either remain dormant (e.g., may not carry asignal to circuitry external to the fan), or may carry a fault signalfrom the fan 102 to external circuitry such as the fan control component204 illustrated in FIG. 2, herein. In contrast, responsive to receipt,by the first pin 103, of a PWM signal within a second PWM range, thesecond pin 105 can carry information corresponding to the fan 102 toexternal circuitry.

The information corresponding to the fan 102 that may be carried by thesecond pin 105 in response to receipt of the PWM signal within thesecond PWM range by the first pin 103 can include, but is not limited tostatic data and/or telemetry data. As used herein, “static data” refersto data that could be provided as part of a manufacturer's data sheetand/or could be pre-programmed into the fan 102 prior to sale of thefan. Non-limiting examples of static data include an identification ofthe manufacturer or vendor, a revision number, a manufacturing datecode, a barcode, a serial number, a nominal fan operation voltage,maximum current rating data for the fan, maximum RPM data for the fan,and/or other information that may be used to identify or otherwisecharacterize the fan 102.

As used herein, “telemetry data” refers to data that may be sensed oraggregated by the fan over time, such as environmental data and/oraggregated performance data. Non-limiting examples of telemetry datainclude fan bearing lifetime data, airflow data (e.g., cubic feet perminute data), pressure data, humidity data, temperature data, a numberof faults experienced by the fan 102, how many hours the fan 102 hasbeen in operation, an amount of power consumed by the fan over timeand/or instantaneously, and/or other information that can be aggregatedover time by the fan 102. In some examples, the telemetry data can beused to optimize performance of the fan 102. The telemetry data can becollected by a sensor associated with the fan, such as the sensor 110illustrated in FIG. 1B, herein.

A third pin 107 can be a voltage pin to receive a power signal (e.g.,+12 volts, +5 Volts, +3.3 Volts, etc.) to provide power to the fan 102.In some examples, a fourth pin 109 can be a around pin to provide aground reference potential to the fan 102.

As noted above, in some examples the fan 102 may have one or moresensors 110 associated therewith. Such an example is illustrated in FIG.1B. The apparatus 100 illustrated in FIG. 1B may be the same as theapparatus 100 illustrated in FIG. 1A, except for the addition of thesensor(s) 110, and thus the same reference numbers are used herein torefer to their similar components. The components of the apparatus 100′that are the same as the components of the apparatus 100 will not bedescribed again, to avoid duplicative description. The fan 102 and/orthe sensor(s) 110 can be separately considered an “apparatus.”

The sensor 110 can be a device and/or sub-system that can detect eventsor changes in its environment or environmental parameters (such astemperature, pressure, etc.) and store and/or transfer the informationto another component. Specifically, the sensor(s) 110 may collect someor all of the telemetry data described above (or raw data from which thetelemetry data may be deduced). The sensor(s) 110 may store data sensedthereby, send the sensed data to the control circuitry 117 to be stored,send the sensed data to an external controller, or some combinationthereof. As discussed above, the telemetry data collected by the sensor110 can include data that may be sensed or aggregated by the fan 102over time, such as environmental data and/or aggregated performancedata. In some examples, the sensor 110 can send information such astelemetry information collected thereby to a fan control component suchas fan control component 204 illustrated in FIG. 2, herein.

FIG. 2 illustrates a block diagram in the form of an example apparatus201 including a fan control component 204 consistent with thedisclosure. The fan control component 204 may be a fan controller thatis external to the fan 102 and that controls the fan 102 by providingpower to and/or sending signals to the fan 102, for example via the pins103, 107, and 109. The fan control component 204 may also receiveinformation from the fan 102, for example, via the pin 105. For example,the fan control component 204 may be a fan controller and/or baseboardmonument controller (BMC) of a computing device, such as a server.

The fan control component 204 may include control logic 206 that isconfigured to perform (or cause performance of) the operations describedherein in relation of the fan control component 204, includingtransmission of signals to a fan to initiate transfer of informationfrom the fan and receipt and/or processing of the information receivedin response to the transmitted signals. For example, the fan controlcomponent 204 can be configured to perform tasks and/or functions tocontrol operation a fan (e.g., fan 102 illustrated in FIG. 1, herein),receive information corresponding to a fan, process the receivedinformation, analyze the received information, and/or cause the receivedinformation to be tabulated and/or displayed (e.g., by a graphical userinterface), as described in more detail, herein. In some examples, theinformation corresponding to the fan 102 can be processed to determinestatistical, analytical, or big data information corresponding to thefan 102.

The control logic 206 may include a processing resource and instructionsexecutable thereby (e.g., computer code, firmware, software, machinecode, etc.), or dedicated hardware/circuitry, or any combinationthereof. A “processing resource” may include any circuitry that iscapable of executing machine readable instructions, such as a processor,baseboard management controller (BMC), CPU, system-on-chip (SoC),digital signal processer, etc. “Dedicated hardware/circuitry” mayinclude any hardware and/or circuitry that is configured to performspecific functions, such as an application specific integrated circuit(ASIC), field-programmable gate array (FPGA), complex programmable logicdevice (CPLD), etc.

In some examples, the fan control component 204 can be operable totransmit a pulse width modulated signal having a particular duty cycleto a particular signal pin of a fan, such as the fan 102 illustrated inFIG. 1, herein. The particular signal pin of the fan can be a PWM signalpin of the fan such as the first pin 103 illustrated in FIG. 1, herein.The PWM signal having the particular duty cycle can comprise a faninformation request signal such as the fan information request signal534 illustrated in FIG. 5, herein, which can operate as a request and/orinstruction to the fan for information corresponding to the fan.

The particular (e.g., second) PWM range can correspond to an upper PWMrange receivable by the fan. For example, the particular PWM range cancorrespond to an upper 10% of the total PWM signal range receivable bythe fan, as discussed in more detail in connection with FIG. 4, herein.Examples are not so limited, however, and in some examples, theparticular PWM range can correspond to a particular PWM digital encodingvalues such as 230-255 PWM. Further, in some examples, the particularPWM range can correspond to greater than (or less than) the upper 10% ofthe total PWM signal range receivable by the fan. For example, theparticular PWM range can correspond to 5% of the upper range, 15% of theupper range, etc.

The fan control component 204 can be operable to receive informationcorresponding to the fan in response to transmission of the signal. Forexample, the fan control component 204 can be operable to receiveinformation corresponding to the fan in response to transmission of thesignal having a PWM range corresponding to the particular duty cycle toa particular signal pin of a fan. As described above, the informationcorresponding to the fan can include information regarding the fan'svendor, manufacture date, serial number, bar code, revision number,and/or other information that may be used to identify or otherwisecharacterize the fan.

The fan control component 204 can, in some examples, cause a diagnosticoperation to be performed on the fan based on the informationcorresponding to the fan. For example, the fan control component 204 canprocess the information corresponding to the fan to analyze the fan'sperformance to track, analyze, troubleshoot, or otherwise tally and/orremedy faults or performance issues of the fan.

In some examples, the fan control component 204 can transmit a signalhaving a duty cycle that is in a particular range that corresponds to aduty cycle that is different than the particular duty cycle describedabove. For example, the fan control component 204 can transmit a signalthat has a duty cycle that is within a lower PWM range than theparticular PWM range. The lower PWM range can, in some examples, be aPWM range that is lower than 90% of the total PWM range receivable bythe fan. In some examples, receipt of the signal that has the duty cyclewithin the lower PWM range than the particular PWM range can cause thefan to operate in a normal cooling mode of operation. In some examples,in the normal cooling mode of operation, the fan controls its speedbased on the duty cycle of the PWM signal. Thus, the PWM signal may beconsidered to be a fan speed control signal when its duty cycle isoutside the particular PWM range, and may be considered to be a requestor instruction to transmit information about the fan when its duty cycleis inside the particular PWM range.

FIG. 3 illustrates a block diagram in the form of an example system 311including the fan 102 and the fan control component 204. The fan 102 isan instance of the fan 102 illustrated and described in connection withFIG. 1, while the fan control component 204 is an instance of the fancontrol component 204 illustrated and described in connection with FIG.2. In some examples, the fan 102 or the fan control component 204 canseparately be considered an “apparatus.”

The fan 102 and the fan control component 204 can be communicativelycoupled via a communication link 312. The communication link 312 can bea physical communication link, such an interface, wire, or otherphysical communication path to provide communication between the fan 102and the fan control component 104. Although shown as a single entity,the communication link 312 can comprise multiple communication links to,for example, facilitate transmission and receipt of signals to the pins103, 105, 107, and 109 of the fan 102 illustrated in FIG. 1, herein.

Although shown as discrete components in FIG. 3, the fan 302 and the fancontrol component 304 need not be discrete and can, for example, bedisposed or deployed on a single component such as an integrated circuitor contiguous printed circuit board.

FIG. 4 illustrates a curve 420 depicting an example of revolutions perminute (RPM) versus duty cycle of a PWM signal consistent with thedisclosure. Specifically, the fan 102 may be configured to control itsspeed (i.e., RPM) based on the duty cycle of the PWM signal received atthe first pin 103, and the curve in FIG. 4 illustrates one possiblerelationship between RPM and duty cycle that the fan 102 may beconfigured to use. As shown in FIG. 4, a range of RPMs for a fan (e.g.,the fan 102 illustrated in FIG. 1) are shown on the y-axis of the curve420, while the total range of possible duty cycles for the PWM signalthat can be provided to the fan are is shown on the x-axis of the curve420.

As shown in FIG. 4, in some examples, a first PWM range 422 correspondsto duty cycles between around 5% and 90% of a total PWM range receivableby the fan. A second PWM range 422 corresponds to PWM signals betweenaround 90% and 100% of the total PWM range receivable by the fan. A MaxRPM (e.g., a maximum RPM at which the fan can operate) corresponds tothe highest duty cycle value of the second PWM range 422 (e.g. about90%), but not the highest possible duty cycle value (e.g., 100%). Thisis in contrast to many other approaches, in which the MAX RPMcorresponds to the highest possible duty cycle value. A Min PRM (e.g., aminimum RPM at which the fan can operate, which may be greater than zeroRPM) corresponds to a lowest duty cycle value of the second PWM range422 (e.g., about 5%), which is not necessarily the lowest possible dutycycle value (0%). Thus, various RPMs at which the fan can operatecorrespond to duty cycle values that fall within the first PWM range422.

In some examples, the lowest PWM ranges shown in the curve (e.g.,between 0% PWM and around 5% PWM) can correspond to a grace periodduring which a PWM signal is asserted to the fan, but the fan has notyet began operating. Some approaches have proposed utilizing this lowestrange to initiate a transfer of information corresponding to the fan,however, such approaches could eliminate the grace period, which canlead to an increased chance that the fan misinterprets a fan informationrequest signal. This can lead to inaccuracies or other problems inreliably initiating a transfer of information from the fan.

In some examples, the second PWM range 424 can correspond to theparticular PWM range described in connection with FIGS. 1, 2, and 3,herein. For example, the second PWM range 422 can correspond to a dutycycle of a PWM signal being in a range that, when asserted to a PWMsignal pin (e.g., pin 103 illustrated in FIG. 1, herein), can cause thefan to transmit information corresponding to the fan via a fault signalpin (e.g., pin 105 illustrated in FIG. 1, herein).

By reserving the second PWM range 424 for initiation of an operation totransfer information corresponding to the fan, it may be possible toreduce or eliminate a chance that the fan either continues normaloperation instead of initiating the transfer of information, or it maybe possible to reduce or eliminate transmission of a fault (e.g., anerror) signal being transmitted from the fan.

FIG. 5 illustrates an example timing diagram 530 including a faninformation request signal 534 consistent with the disclosure. As shownin FIG. 5, a PWM signal having a first duty cycle 532 is being appliedto a fan (e.g., fan 102 illustrated in FIG. 1, herein). In the exampleof FIG. 5, the first duty cycle of the PWM signal 532 is about 30%, butthis is just one example. In some examples, the signal is asserted to aPWM pin of the fan such as the first pin 103 illustrated in FIG. 1,herein. The duty cycle of the PWM signal 532 falls within a first PWMrange (e.g., the first PWM range 422 illustrated in FIG. 4, herein) andtherefore in response to receipt of the PWM signal 532, the fan mayoperate in a normal mode of operation. Stated alternatively, in responseto receipt of the PWM signal 532, the fan may operate to provide fluidflow to a computing component and/or a computing system. For example,the fan may operate at a speed that is based on the duty cycle of thePWM signal 532.

At some point in time, a fan information request signal 534 can beasserted to the PWM pin of the fan. The fan information request signal534 can have a different duty cycle than the first duty cycle 532 of thePWN signal 532—specifically, the duty cycle of the fan informationrequest signal 534 falls within a second PWM range (e.g., the second PWMrange 424). In the example, of FIG. 5, the duty cycle of the faninformation request signal 534 is shown as a 100% duty cycle, but thisis merely one example. In some examples, the PWM signal 532 that has thefirst duty cycle and/or the PWM signal that corresponds to the faninformation request signal 534 can be asserted by a fan controlcomponent such as the fan control component 204 illustrated in FIG. 2,herein.

As noted above, the fan information request signal 534 is a PWM signalwhose duty cycle falls within a second PWM range (e.g., the second PWMrange 424 illustrated in FIG. 4, herein), and therefore, the faninformation request signal 534 may cause the fan to initiate a transferof information corresponding to the fan as described in connection withFIGS. 1-3, herein. The fan information request signal 534 may beasserted for a threshold period of time, which may span multiple PWMpulse periods. In a non-limiting example, the fan information requestsignal 534 may be asserted for around 500 milliseconds (ms). Assertingthe fan information request signal 534 for multiple PWM periods mayassist in distinguishing between signals that cause the fan to operatein the normal mode of operation and signals that cause the fan totransfer information corresponding thereto. In FIG. 5, because the faninformation request signal 534 has a duty cycle of 100% and is assertedfor multiple periods, it appears as one pulse spanning those multipleperiods. However, in examples in which the fan information requestsignal 534 has a duty cycle less than 100% and spans multiple PWMperiods, it may appear as a string of multiple pulses.

In some examples, during assertion of the fan information request signal534, the fan may continue to operate in the normal mode of operation soas to continue to provide fluid flow to the computing components and/orcomputing system in which the fan is deployed. For example, the fan maycontinue to operate at a same speed prior to, during, and/or afterassertion of the fan information request signal 534. For example, thefan may remember the duty cycle of the PWM signal that was receivedimmediately prior to the fan information request signal 534, and maycontrol its speed based on that duty cycle until a new PWM signal havinga duty cycle in the first range is received. In addition to, or in thealternative, the fan can lock its operation at a current RPM as soon asit recognizes the fan information request signal 534 (e.g., prior toinitiation of the data transfer). This can allow for the fan to continueoperating normally during the data transfer operation(s) as opposed tooperating with varying speed, which may result in sub-optimalperformance.

FIG. 6 illustrates an example timing diagram 631 including a faninformation request signal 634 and information transfer sequence 638consistent with the disclosure. As shown in FIG. 6, a PWM signal thathas a first duty cycle 632 can be asserted to a PWM pin of a fan (e.g.,the first pin 103 of the fan 102 illustrated in FIG. 1, herein). The PWMsignal that has the first duty cycle 632 can cause the fan to operate ata particular speed (e.g., at a particular RPM). The first duty cycle 632may falls within a first PWM range (e.g., the first PWM range 422illustrated in FIG. 4, herein). In response to receipt of the PWM signalcorresponding to the first duty cycle 632, the fan may operate in anormal mode of operation.

At some point in time, a fan information request signal 634 can beasserted to the PWM pin of the fan. The fan information request signal634 can be characterized as having a different duty cycle than the firstduty cycle 632 associated therewith, as indicated by the difference inwidth along the x-axis of the fan information request signal 634 versusthe first duty cycle 632. Responsive to assertion of the fan informationrequest signal 634, a pre-amble signal 636 having a particular time(e.g., a PA time 637) associated therewith may be asserted on a faultsignal pin of the fan. It is however noted that, in some examples, thepre-amble signal 636 is not asserted on the fault signal pin of the fan.The fault signal pin of the fan may correspond to the second pin 105illustrated in FIG. 1, herein.

In some examples, a delay 635-1 may be provided subsequent to assertionof the fan information request signal 634 on the PWM pin and assertionof the pre-amble signal(s) 636 on the fault signal pin. The pre-amble636 may be provided to signal to the fan or to a fan control component(e.g., the fan control component 204 illustrated in FIG. 2, herein)coupled to the fan that the fan is ready to begin transmission ofinformation corresponding to the fan and/or that the fan controlcomponent is ready to begin receipt of information corresponding to thefan via the fault signal pin.

In some examples, the pre-amble signal 636 can include one or moresignal pulses that last for a particular period of time. For example, ina non-limiting example, the pre-amble signal 636 can include two signalpulses that last for around 720 ms each.

Subsequent to assertion of the pre-amble signal 636, one or more delays635-N may be provided to the fault signal pin. Subsequent to a finaldelay 635-N, an information transfer sequence 638 may be asserted on thefault signal pin. The delays 635-1, . . . , 635-N can last for differentperiods of time or for the same period of time. In one non-limitingexample, the first delay 635-1 can last for around 500 ms, while thesecond delay 635-N can last for around 250 ms.

The information transfer sequence may have one or more transferintervals, such as transfer interval 639 associated therewith. Thetransfer intervals 639 can include assertion of signals for differentperiods of time. For example, the transfer interval can be around 180ms, however, examples are not limited to this particular example. Insome examples, the information transfer sequence 638 allows the fancontrol component to receive information corresponding to the fan. Asdescribed above, the information can include information correspondingto a manufacturer, model, revision number, serial number, barcode, orother information that may serve to identify characteristics of the fan.

In some examples, the information corresponding to the fan can beformatted in time domain multiplexed bits. For example, as shown in FIG.6, during the information transfer sequence 638, the signal asserted onthe fault signal pin can alternate between a HIGH value (correspondingto a logical value of “1”) and a LOW value (corresponding to a logicalvalue of “0”). The fan control component can, in some examples,interpret these values to ascertain information corresponding to thefan.

In some examples, the information corresponding to the fan can betransferred in accordance with a particular specification or protocol,such as the SMBus 2.0 specification. For example, the informationcorresponding to the fan can, for example, be transferred in 64-bytepackets in accordance with the CRC-8 specification. Such specificationscan allow for error checking to be performed on the packet containingthe information corresponding to the fan to ensure data integrity.

It is noted that, in the example of FIG. 6, the speed of the fan (e.g.,the RPM at which the fan operates) remains constant throughout assertionof the PWM signal corresponding to the first duty cycle 632, assertionof the fan information request signal 634, the delays 635-1, . . . ,635-N, the pre-amble 636, and the information transfer sequence 638.This may allow the fan to continue to operate in the normal mode ofoperation so as to continue to provide fluid flow to the computingcomponents and/or computing system in which the fan is deployed duringthe performance of the operations illustrated in FIG. 6.

FIG. 7 illustrates an example machine-readable medium 740 for a pulsewidth modulation fan consistent with the disclosure. The example medium740 may store instructions 741 executable by a processing resource suchas a hardware computer processor to cause a computing system to performcertain tasks and/or functions, as described herein. The non-transitorymachine readable medium 740 may be any type of volatile or non-volatilememory or storage, such as random-access memory (RAM), flash memory,read-only memory (ROM), storage volumes, a hard disk, or combinationsthereof.

The example medium 740 may store instructions 742 executable by theprocessing resource to cause a pulse width modulated (PWM) signal havinga duty cycle that falls within a first duty cycle range to be assertedon a control pin of a fan to control a speed of the fan. The PWM pin ofthe fan can correspond to the first pin 103 of the fan 102 illustratedin FIG. 1, herein.

The example medium 740 may store instructions 744 executable by theprocessing resource to cause a PWM signal having a duty cycle that fallswithin a second duty cycle range to be asserted on the control pin ofthe fan to request information corresponding to the fan to betransferred to a controller external to the fan. The signal may be asignal to request information from the fan, such as the fan informationrequest signal 534 illustrated in FIG. 5, herein. In some examples, theinformation may be received by a fan control component (e.g., fancontrol component 204 illustrated in FIG. 2, herein) via a fault signalpin such as the second pin 105 of the fan 102 illustrated in FIG. 1,herein.

The second duty cycle range can correspond to the second PWM range 424illustrated in FIG. 4, herein. In some examples, the processing resourcecauses a PWM signal having a particular duty cycle to be generated bycommunicating a digital value that represents the particular duty cycleto a signal generator. The digital value used by the processing resourcemay be referred to herein as a PWM value. The processing resource mayuse any mapping of PWM values to duty cycles, For example, if theprocessing resource uses 8 bits for the PWM values, then there are 256possible PWM values that can represent 256 possible duty cycles. Forexample, if the values are mapped in assenting order, then 0 PWM wouldrepresent a duty cycle of 0% and 255 PWM would represent a duty cycle of100%. In such an example, the second range may correspond to PWM valuesof 230 to 255 PWMs, since 230 PWM represents approximately 90% dutycycle and 255 PWM represents approximately 100% duty cycle. The PWMsignal can further correspond to an initiation signal such as the faninformation request signal 534 and 634 illustrated in FIGS. 5 and 6,respectively, herein.

In some examples, the example medium 740 may store instructions 741executable by the processing resource to cause the computing system toprocess the information requested from the fan to determine static data,telemetry data, or combinations thereof, corresponding to the fan. Forexample, the example medium 740 may store instructions 741 executable bythe processing resource to determine static data such as a fan vendor, arevision number, a manufacturing date code, a bar code, an error code,or combinations thereof corresponding to the fan and/or telemetry datasuch as data corresponding to environmental conditions of the fan.

The example medium 740 may store instructions 741 executable by theprocessing resource to cause the computing system to cause theinformation corresponding to the fan to be displayed via a graphicaluser interface (GUI). For example, the instructions 741 may beexecutable by the processing resource to generate a GUI and/or populatea GUI with a fan vendor, a revision number, a manufacturing date code, abar code, a fan vendor, a revision number of the fan, a manufacturingdate code of the fan, a bar code of the fan, a serial number of the fan,etc.

In some examples, the example medium 740 may store instructions 741executable by the processing resource to cause the computing system toperform a diagnostic operation on the fan based, at least in part, onthe received information corresponding to the fan. The diagnosticoperation may include troubleshooting, tracking, and/or analyzinginformation corresponding to the fan to remediate performance issues thefan may be experiencing.

In the foregoing detailed description of the disclosure, reference ismade to the accompanying drawings that form a part hereof, and in whichis shown by way of illustration how examples of the disclosure may bepracticed. These examples are described in sufficient detail to enablethose of ordinary skill in the art to practice the examples of thisdisclosure, and it is to be understood that other examples may beutilized and that process, electrical, and/or structural changes may bemade without departing from the scope of the disclosure. As used herein,designators such as “N”, etc., particularly with respect to referencenumerals in the drawings, indicate that a number of the particularfeature so designated can be included. A “plurality of” is intended torefer to more than one of such things. Multiple like elements may bereferenced herein by their reference numeral without a specificidentifier at the end.

The figures herein follow a numbering convention in which the firstdigit corresponds to the drawing figure number and the remaining digitsidentify an element or component in the drawing. For example, referencenumeral 102 may refer to element “02” in FIG. 1 and an analogous elementmay be identified by reference numeral 202 in FIG. 2. Elements shown inthe various figures herein can be added, exchanged, and/or eliminated soas to provide a number of additional examples of the disclosure. Inaddition, the proportion and the relative scale of the elements providedin the figures are intended to illustrate the examples of thedisclosure, and should not be taken in a limiting sense.

What is claimed:
 1. An apparatus, comprising: a fan including a controlpin, the fan to: receive a pulse width modulated (PWM) signal at thecontrol pin; control a speed of the fan based on a duty cycle of the PWMsignal when the PWM signal is in a first range; and responsive to theduty cycle of the PWM signal being in a second range, transmitinformation corresponding to the fan to an external controller.
 2. Theapparatus of claim 1, wherein the PWM signal being in the second rangeinclude the PWM signal being in a range that spans about 10% of a totalPWM signal range receivable by the control pin.
 3. The apparatus ofclaim 1, wherein the information corresponding to the fan includesstatic data, telemetry data, or combinations thereof.
 4. The apparatusof claim 1, wherein the fan is to operate at a same speed when the PWMsignal is in the first range and when the PWM signal is in the secondrange.
 5. The apparatus of claim 4, wherein the fan further comprisescontrol circuitry to lock the speed of the fan responsive to the dutycycle of the PWM signal being in the second.
 6. The apparatus of claim1, wherein the fan further comprises a sensor to detect a change in anenvironment of the fan.
 7. The apparatus of claim 1, wherein the fan isto transmit information corresponding to the fan via a fault signal pinof the fan.
 8. An apparatus, comprising: a fan control componentincluding a processing resource and operable to: control operation of afan based, at least in part, on a duty cycle of a pulse width modulated(PWM) signal when the duty cycle of the PWM signal is in a first range;and request information corresponding to the fan based, at least inpart, on the duty cycle of the PWM signal being in a second range. 9.The apparatus of claim 8, wherein the fan control component is to causethe information corresponding to the fan to be processed to determinestatistical information, analytical information, or combinationsthereof, associated with the fan.
 10. The apparatus of claim 8, whereinthe information corresponding to the fan includes static data, telemetrydata, or combinations thereof.
 11. The apparatus of claim 8, wherein theduty cycle of the PWM signal being in the second range includes the dutycycle of the PWM signal spanning about 10% of a full duty cycle.
 12. Theapparatus of claim 8, wherein the duty cycle being in the second rangeincludes the duty cycle being within an upper range of a total pulsewidth modulation range receivable by the particular signal pin.
 13. Theapparatus of claim 8, wherein the fan control component is to requestinformation from the fan to be transmitted from a fault signal pin ofthe fan.
 14. The apparatus of claim 8, wherein the fan control componentis to cause a diagnostic operation to be performed on the fan based, atleast in part, on the received information corresponding to the fan. 15.A non-transitory machine-readable medium storing instructions executableby a processing resource to cause a computing system to: cause a pulsewidth modulated (PWM) signal corresponding to a first duty cycle rangeto be asserted on a control pin of a fan to control a speed of the fan;cause a PWM signal corresponding to a second duty cycle range to beasserted on the control pin of the fan to request informationcorresponding to the fan to be transferred to a controller external tothe fan.
 16. The non-transitory machine-readable medium of claim 15,wherein the instructions are further executable to cause the computingsystem to cause the PWM signal corresponding to the second duty cycle tospan about 10% of a full duty cycle.
 17. The non-transitorymachine-readable medium of claim 15, wherein the instructions arefurther executable to cause the computing system to process theinformation requested from the fan to determine static data, telemetrydata, or combinations thereof, corresponding to the fan.
 18. Thenon-transitory machine-readable medium of claim 15, wherein theinstructions are further executable to cause the computing system tocause the information corresponding to the fan to be displayed via agraphical user interface.
 19. The non-transitory machine-readable mediumof claim 15, wherein the instructions are further executable to causethe computing system to perform a diagnostic operation on the fan based,at least in part, on the received information corresponding to the fan.20. The non-transitory machine-readable medium of claim 15, wherein theinstructions are further executable to cause the computing system tocause the fan to operate at a same speed that is was operating atimmediately prior to the PWM signal having the second duty cycle rangebeing asserted on the control pin of the fan.